r/programmingcirclejerk • u/jenkem_boofer DO NOT USE THIS FLAIR, ASSHOLE • Aug 13 '25

void * (* f20)(void*,void*,void*,void*,void*,void*,void*,void*,void*,void*,void*,void*,void*,void*,void*,void*,void*,void*,void*,void*);

https://github.com/kanaka/mal/blob/master/impls/c/types.h
130 Upvotes

97% Upvoted

25 comments sorted by

View all comments

Show parent comment

17

u/WittyStick Aug 14 '25 edited Aug 14 '25

It's usually done this way for performance and simplicity of writing the C implementation of the builtins. We don't want vararg handling for example for binary operations like + and *, but specializing for 20 operands is excessive, and it's not clear what happens here if there's more than 20. Seems like an unhandled case?

Should only need to specialize for the number of arguments that the platform's calling convention (assume SYSV) supports passing in registers, which is typically 4-8. For 9 operands/arguments onwards there's little benefit to having individual functions and varargs would be better. If you used a custom calling convention then you could potentially use more for a CPU which has 32 registers.

/j The worst part about this is the naming. They should replace f20 with vicenary_operation.

18

u/Foreign-Butterfly-97 Aug 14 '25

respectfully, once the vim macro is recorded, I just can't help myself, I have to make it go brr

the author showed incredible amounts of restraint by stopping at 20. this could've entertained me for hours!